While optical microscopy and other optics-based methods have been exploited in many domains of human activity, from scientific research to warfare for many hundreds of years, the advent of microprocessors, modern computing, and molecular biology have given rise to an ever-accelerating development of new optical instrumentation and optical-imaging technologies. For example, fluorescent tagging of proteins within living cells, combined with computational facilities incorporated in modern fluorescence-microscopy instrumentation allows fine detail of biological components of living cells to be imaged at resolutions significantly lower than the so-called “diffraction limit” for optical microscopy.
Many new optical instruments, applications of optical instruments, and optical-imaging technologies depend on precise focusing of high-powered optical systems with shallow depths of focus over prolonged periods of time and/or during scanning of imaged objects within the x-y plane orthogonal to the optical z axis. Examples include various optical-microscopy techniques that achieve below-diffraction-limit resolution by imaging weakly emitting fluorophores in biological samples over relatively long periods of time and optical-microscopy techniques for scanning living cells and other biological samples to image planes within these samples by translating the samples in the x-y plane with respect to the optical path of the microscope while maintaining a constant z position. The focus of optical instruments may vary, over time, as a result of thermal and electromechanical instabilities, for example, and even very precise electromechanical microscope stages may fluctuate, in distance with respect to imaging optics, as the stage is translated in the x-y plane while scanning samples or while collecting data from samples over periods of time. Designers, manufacturers, and users of precision optical instrumentation continue to seek systems and methods that stabilize the focus of high-precision optical instruments over time and while the various subcomponents of the high-precision optical instruments, including electromechanical stages, are operating.